Method and apparatus for plugging furnace taps

ABSTRACT

A method of using wooden plugs to plug tapholes through which slag and metal are periodically removed from phosphorous furnaces and the like. In accordance with the method, green, wooden plugs are inserted into drilled tapholes and the hot material discharging from the furnace burns all or part of the plugs to form a charcoal plug. The hot material most remote from the center of the furnace cools and solidifies to form even more permanent plugs as it moves into the tapholes and as the wooden plugs are burned and charred.

United States Patent Elwin L. Smith 720 Balsam, Pocatello, Idaho 83201 826,477

May 21, 1969 Aug. 17, 1971 Inventor Appl. No. Filed Patented METHOD AND APPARATUS FOR PLUGGING FURNACE TAPS 7 Claims, 4 Drawing Figs.

11.8. C1 266/42, 13/33, 23/223, 23/277 lnt.Cl C2lb 7/12 FieldofSearch 13/33,35; 266/38, 42; 23/223, 277; 75/28, 65, 132

References Cited UNITED STATES PATENTS 1/1907 Landis 13/33 1,277,899 9/1918 Freeman 13/33 2,509,228 5/1950 Hardin 23/223 3,398,945 8/1968 Walpole 266/42 Primary Examiner-Gerald A. Dost Attorney-B. Deon Criddle ABSTRACT: A method of using wooden plugs to plug tapholes through which slag and metal are periodically removed from phosphorous furnaces and the like. In accordance with the method, green, wooden plugs are inserted into drilled tapholes and the hot material discharging from the furnace burns all or part of the plugs to form a charcoal plug. The hot material most remote from the center of the furnace cools and solidifies to form even more permanent plugs as it moves into the tapholes and as the wooden plugs are burned and charred.

PATENTE-l] MIG] 712m FIG I FIG 2 INVENTOR. ELWIN L. SMITH ATTORNEY METHOD AND APPARATUS FOR PLUGGEIG FURNACE 'FlAlPS BACKGROUND OF THE INVENTION Field of the Invention This invention relates to furnaces such as phosphorous furnaces that must be periodically tapped at different levels to remove accumulated molten metal and slags and is particularly concerned with providing a relatively safe, inexpensive way of plugging such tapholes after desired amounts of the molten material have been removed, and of providing unique plugs for use in plugging such tapholes.

lrior Art it has long been common in the production of phosphorous to utilize high-temperature electrode furnaces into which ore to be treated is fed. The ore is heated in an oxygen free atmosphere to very high temperatures, the gasses generated are carried oft and a lower layer of molten metal, which may include ferre phos and other metals and an upper layer of molten slag which may include silica, coke, and shale, for example, are formed. it has been common to periodically drill tapholes through the wall of the furnace so that the accumulated layers of molten metal and slag can drain out of the furnace and into pits formed in a surrounding sand field where they can cool and solidify. To make the tap through a hardened clay plug an overhead crane mounted, long pneumatic, rotary drill is generally initially used. This drill is moved into place and an initial penetration is made. lf, as sometimes happens, however, the drill inadvertently completes the borehole it may get stuck and then invariably will be damaged by the molten material. Desirably, however, only a partial penetration is made with the drill and it is then withdrawn and moved away. A long pipe forming an oxygen lance and made of replaceable sections is next used to transmit oxygen, which is ignited at the end of the pipe and that is then inserted into the borehole to burn through the remaining portion of the plug. During this operation as many as six to eight lengths of pipe section may be destroyed before the hole is completed, and, in addition, the carbon sleeve through which the tap is made is severely worn. As a result of this type of wear, the carbon sleeves must commonly be replaced every 4 to 6 months.

Because of the molten and highly flammable nature of the materials and because the molten metal will explode if put in contact with water, it has not been unusual in the past that workmen responsible for tapping off the slag and metals, and of plugging the tapholes when the draining was complete, have been severely burned. The making of a tap using the long rotary drill and/or a long oxygen lance and the subsequent plugging has required a crew of men who must move close the the taphole where they can perform the drilling and can insert a moist clay material that will cement itself to the walls of carbon sleeves through the refractory brick walls of the furnace as it dries and that will then form a complete barrier within the hole. The moisture in the clay must be rigorously controlled and the plug must be carefully formed.

The plugging of the tapholes with clay is an expensive and somewhat time consuming process since it requires a mud mill to produce the proper consistency of clay and as many as three clay plugs must be prepared in advance of each plugging operation. Then if none of the prepared plugs can be satisfactorily inserted, others may have to be prepared and furnace efficiency may be greatly affected. To reduce the chance ofinjuries occuring while a clay plug is inserted, it is generally necessary to raise the furnace electrodes or to cut the electricity to the electrodes, thereby slowing or stopping the reaction. In at least one plant, this has meant an operational stoppage or downtime of as much as 10 minutes during each tap plugging operation. Since the electricity is generally paid for on a contract basis and is delivered, whether or not it is continuously used, the failure to use the delivered electricity can be very costly.

Even after the clay plug has been inserted, there is always a possibility that there will be a subsequent break out" when the molten material seeps through and opens up the plug.

SUMMARY OF THE INVENTION The present invention provides a method whereby fewer personnel are required to plug tap openings and whereby personnel are less exposed to the dangers of the open tapholes for a much shorter period of time. In fact, with the invention, plugging can generally be accomplished so quickly and easily that it is not necessary to raise the furnace electrodes or to cut off the electricity to the electrodes during the plugging operation. In addition, less oxygen is required by the oxygen lance to reopen holes plugged according to the method of the invention and the life of the carbon sleeves through which the tap is made is greatly extended. The method involves the use of green wood plugs that are inserted into the tapholes and that are allowed to char until blocks of charcoal are formed and the furnace material acting on them solidifies, to itself form a plug for the hole.

One man or two men can easily insert a wooden plug of the invention from behind a protective barrier and with much less chance of receiving personal injury from burns than could previously be achieved when a crew of men had to be in a fully exposed position as they put clay into the tapholes. Furthermore, the borehole through the carbon sleeves into which the wood plug is inserted stays small for a longer period of time, thereby reducing the possibility of injuries due to furnace pressure rupturing or blowing the plug out.

Because of the reduced number of men required, because fewer injuries result and because it is no longer necessary for one man to spend a great deal of time at the clay mill in advance of a plugging operation to prepare a number of clay plugs so that if one or more fail others will be ready for use, it has been found much more economical to use more reliable wooden plugs, instead of clay, even though the cost of the plugs per se may exceed the cost of the clay per se.

Also, since as has been noted, it is much easier and faster to insert wooden plugs that have been prepared and stocked well in advance, there is little if any costly downtime of the furnaces. Another cost savings results from the shorter drill time required to drill through the remains of the wood plugs and/or the solidified plug formed in accordance with the invention, in comparison to the time required to drill through a mud plug. With the present invention an oxygen lance can be used to blow out the charcoal and the lance will thereafter quickly cut through the barrier formed by solidified material. Complete penetration is made quickly, without any requirement for initial boring with a rotary drill, and with only three to five sections of the pipe making up the lance being destroyed during the operation. This greatly reduces the cost of oxygen and of pipe required to reopen a taphole. Also, because the tapholes can be opened so quickly there is little danger that an overaccumulation of slag and metal will develop inside the furnace during the tapping operation. Such an accumulation, if it occurs, can be very dangerous since the molten metal may then flow out a slag hole and come in contact with water to thereby create a dangerous explosion. These factors also contribute to the overall savings resulting from use of the present method.

In practicing the method of the invention, wooden plugs made of uncured wood, without cracks or flaws therein, are tapered to be easily but tightly inserted into the tapholes and to plug the holes. If desired, a feedpipe or rod can be inserted into a hole provided therefore in the end of the plugs and can be used to support and direct the plugs as they are inserted into the hole. The pipe or rod can then be used to push the wood plugs in and to hold them until they have charred and until an additional permanent plug of solidified furnace material has formed.

In any event, the wooden plugs are inserted and are allowed to burn outwardly from the inside of the furnace. As the hot material progresses outwardly through the plugged hole the green wood burns slow enough that it forms a charcoal block and the material cools sufficiently to form a solidified slag or metal mass that then serves as a further permanent plug for the taphole.

The wood plugs, in addition to being shaped with a taper so that they can be easily inserted and will fully plug the taphole, and in addition to being made of green or uncured, relatively dense wood, must be made of wood having no cracks or flaws therein. It has been found that if cracks are present, the molten material will seep into them and will pass through the plug and break through to the outside before it can solidify to form a permanent plug. While other suitably dense and green woods can be used, I have found it desirable to utilize lodge pole pine trees that have been freshly cut. This wood is sufficiently dense and when green, burns sufficiently slow to allow for sealing of the taphole. The plugs are promptly cut to shape from the straight trunks of the freshly felled trees and are soaked in water before being immediately wrapped in plastic, or they may be cut to length, soaked, and buried in moist sawdust until they are later shaped and readied for use. The plastic wrapping is impervious to moisture and thus greatly reduces the rate at which moisture is lost from the shaped plug. Burying the cut lengths in sawdust also reduces evaporation losses and protects the plugs from the drying effects of the sun and wind while providing a convenient means for storing them until shaping is desired. This allows logging operations to be carried on during summer months, for example, when the trees are readily accessible and shaping to take place even during winter months when snow prevents access to the trees. Since the plugs are at all times maintained in their moist green state and are not allowed to dry out, shrinking and accompanying cracking does not occur.

The plugs are each tapered from a small end to a flared head at the opposite end, and in one embodiment a shoulder is provided adjacent the head so that a collar of clay can be used, if desired, to insure even faster and more effective sealing of the plug with the sleeve in the wall of the furnace through which it is inserted, even if the sleeve bore is ofirregular shape.

Additional objects and features of the invention will become apparent from the following detailed description and drawings, disclosing what is presently contemplated as being the best mode of the invention.

THE DRAWINGS FIG. 1 is a side elevation view of a furnace having wooden plugs ofthe invention inserted in the tapholes thereof;

FIG. 2, horizontal section taken on the line 2-2 of FIG. ll;

FIG. 3, a perspective view of one form of wood plug of the invention; and

FIG. 4, a similar view of another embodiment of wooden plug, with a clay collar shown fragmentarily, for clarity.

DETAILED DESCRIPTION Referring now to the drawings:

In the illustrated embodiment of FIGS. I -35, the wooden plugs of the invention are shown generally at 10.

As shown in FIG. 1, the wooden plugs have been inserted through the wall of a phosphorous furnace, shown generally at 12.

The phosphorous furnace includes downwardly extending electrodes I3, feed chutes 14, through which ore is fed to the furnace l2, and a duct 15, through which gasses are removed from the interior of the furnace.

The wall of the furnace is interiorly lined with several courses of refractory brick l6 and the outer shell 17 of the furnace is of stainless steel.

At a predetermined height above the bottom of the furnace a plurality of carbon sleeves 18, that extend through the furnace wall, are spaced around the furnace. The sleeves each have a central bore that serves as a taphole through which molten slag is removed and the sleeves are replaceable as they wear out. In use, the central bores are plugged and the plugs are periodically tapped out, using an oxygen drill, as frequently as may be required to prevent an excessive slag accumulation. In one operation, for example, the tapping through the sleeves 18 occurs approximately every 30 minutes. The oxygen used during the tapping erodes the carbon sleeves at a rapid rate, but by cutting the exposure time of the oxygen to the sleeves, with the present invention, and by using the oxygen to cut through smaller plugs only at the ends of the sleeves, the life of the sleeves is greatly extended. This, of course, means that there is a great cost savings in not having to replace the sleeves so frequently. it also means that a maximum sleeve wall thickness and length is maintained for a greater length of time and there is a much shorter period of time during which the sleeves are apt to be blown out by the pressure in the furnace, with resulting potential injury to workmen.

As has been previously noted, the plugs for the boreholes have, in the past, been formed by stuffing wet clay into the boreholes and allowing it to solidify. This has been very unsatisfactory because of the number of personnel involved, the dangers of which such personnel are subjected, the need to form the clay plug immediately prior to plugging, the costs resulting from excessive downtime during plugging operations, the loss of manpower because of accidents, the excessive oxygen and oxygen pipe used in drilling through clay plugs, and the necessary frequent replacement of the carbon sleeves.

With the present invention, instead of utilizing several men to fill a drilled hole with clay until the passage is completely blocked, a single individual or two men working together can simply insert a tapered wood plug and hold it for a period of time until a solidified slag plug is formed.

The plugs 10 are made ofa suitably dense wood and may be shaped immediately after the wood has been cut and while it is still green. As shown best in FIG. 3, the plugs 10 include a tapered front end 26) that is somewhat blunted at 21, a long, essentially cylindrical intermediate section 22, an enlarged rear end 23 and a flared section 24 connecting the intermediate section and the rear end. The smaller, tapered front end 20 allows the plug to be more easily inserted into the borehole, serves as a guide even though some loose material may be lodged therein. The intermediate section is made only very slightly smaller than the borehole so that it can be easily inserted but so that it will burn back quite slowly. The flared section 24 connects to the enlarged rear end 23, which is larger than the borehole into which the plug is to be inserted,

so that flared section at some point along its length seals the end of the borehole and wedges the plug in place. The operator use a long pipe or rod, not shown, that fits into axial hole 23 a in the enlarged rear end 23 to insert and securely hold the wood plug in place, until the permanent plug has been formed and the wood plug burns until only charred wood is left, In some instances however, the rearmost portion of the plug will not burn completely. This remaining portion is readily removed, either by pulling it from the hole or by blowing it out along with the charred wood, using the oxygen drill. Comparatively little oxygen is required in using the oxygen drill to open the solidified slag plug when it is again necessary to tap the furnace to remove molten slag. If, after the wooden plug is inserted, and the permanent plugs have formed, sand is piled around the protruding end of the wooden plug, oxygen cannot get into the borehole and further charring is stopped. Then when the borehole is again opened, it is only necessary to insert the oxygen lance, blow away the sand and charred wood and at the same time have the hot charred wood ignite the oxygen discharging from the lance. This saves separate igniting of the lance, as previously had to be done prior to tapping of a clay plug. The sand that is used to cover the uncharred portion of the plug is readily available from a field surrounding the furnace and can be supported by chutes used to direct discharge of tapped material to the sand field.

Because of the ease with which the plug can be inserted it is only rarely necessary to cut the electrical power into the furnace. and then only for a very brief time during which the wooden plug is inserted. By contrast, when a clay plug is used, it is absolutely necessary to cut the electricity during each plugging operation and for a longer period of time, during which time the clay is inserted and is allowed to dry.

The same process of plugging, using wooden plugs and allowing the molten material to solidify and form another permanent plug can be used in conjunction with the molten metal taps. These taps are usually not made as frequently as the ones to remove slag, and for example, may be made only once every 8 hours. The sleeves 25, inserted through the furnace wall at the height at which the molten metal is to be drained, are well known, and conventionally have water-jacketed monkeys at their outer ends to receive an expensive water-cooled plug.

The interiors of the sleeves are generally made of carbon and each has a central bore through which the molten metal is drained. The wooden plugs 10 are used with the metal taps in the manner previously described, to form charred plugs as they burn back slowly enough that a permanent solidified metal plug will be formed within the borehole.

As either furnace material, i.e., slag or metal is drained, it is guided by chutes 26 to pits formed in a sand field 27, surrounding the furnace where it is allowed to cool and solidify until it can be easily handled. The chutes 26 are conventional and may be ofsteel, lined with refractory brick.

In FIG. 4, there is shown another embodiment of wooden plug. In this embodiment, the plug, shown generally at 28, has the same tapered end 29, blunted at 30, an intermediate, substantially cylindrical section 31, an enlarged end 32 having an axial hole 32 a therein and a flared section 33 interconnecting the intermediate section and the enlarged end, essentially as was described in connection with plug 10. In this embodiment, however, an inturned shoulder 34 is provided at the junction of the intermediate section 31 and the flared section 33 and another shoulder 35 is provided at the junction of the flared section and the enlarged end.

A collar of moist clay 36, can then be wrapped around the flared section, between shoulders 34 and 35. The inturned shoulder 34 tends to more securely hold the collar since a portion thereof is actually beneath the shoulder.

in use, the plug 28 is used just as is the plug 10, previously described. The collar 36, however, does provide an evenmore complete seal between the outer end of a bore hole into which the plug is inserted and molds to conform to any irregularity in the borehole shape.

While other shapes of plugs can be used, those disclosed have proven especially effective in practicing the method of the invention.

lclaim:

l. A method of plugging tapholes in a phosphorous furnace comprising the steps of forming a slow burning plug to substantially fill the borehole through which molten material is being tapped out and to close the outer end ofthe hole;

protecting the wood plug against its shrinking and cracking before it is inserted into the hole;

inserting the wood plug into the hole such that the outer end ofthe hole is closed;

holding said plug in the hole until a solidified plug is formed from material being tapped from the furnace;

allowing said plug to char back from the end inserted into the borehole, and

blocking admission of air to the charring portion of the wood plug after the solidified plug has formed, whereby portions of the plug remain to resume charring when air is again admitted and an oxygen lance is inserted.

2. A plug for use in tapholes of phosphorous furnaces and the like comprising an elongated wooden member having a tapered end, a straight intermediate section slightly smaller in size than the hole into which it is to be inserted extending from the tapered end, an enlarged end,

a flared section interconnecting the intermediate section and the enlarged end and bore means extending axially into a portion of the straight intermediate through the enlarged end, whereby the plug can be supported on the end of a pole inserted into the said bore to be inserted into a furnace tap hole by an individual standing safely away from the said taphole. 3. A plug as in claim 2, wherein the wooden member is made of green, uncured wood and has no cracks extending through the entire longitudinal length thereof. 4. A plug as in claim 3, wherein the wooden member is made of wood having a density at least as great as that of fresh cut pine. 5. A plug as in claim 2, further including a collar of moist clay surround at least a portion of the flared section. 6. A plug as in claim 2, further including shoulders formed at the junctions of the flared section with the enlarged end and the intermediate section; and a collar of moist clay surrounding the flared section,

between the shoulders. 7. A plug as in claim 6, wherein the shoulder at the junction between the flared section and the intermediate section is turned to more securely hold the clay collar. 

1. A method of plugging tapholes in a phosphorous furnace comprising the steps of forming a slow burning plug to substantially fill the borehole through which molten material is being tapped out and to close the outer end of the hole; protecting the wood plug against its shrinking and cracking before it is inserted into the hole; inserting the wood plug into the hole such that the outer end of the hole is closed; holding said plug in the hole until a solidified plug is formed from material being tapped from the furnace; allowing said plug to char back from the end inserted into the borehole, and blocking admission of air to the charring portion of the wood plug after the solidified plug has formed, whereby portions of the plug remain to resume charring when air is again admitted and an oxygen lance is inserted.
 2. A plug for use in tapholes of phosphorous furnaces and the like comprising an elongated wooden member having a tapered end, a straight intermediate section slightly smaller in size than the hole into which it is to be inserted extending from the tapered end, an enlarged end, a flared section interconnecting the intermediate section and the enlarged end and bore means extending axially into a portion of the straight intermediate through the enlarged end, whereby the plug can be supported on the end of a pole inserted into the said bore to be inserted into a furnace tap hole by an individual standing safely away from the said taphole.
 3. A plug as in claim 2, wherein the wooden member is made of green, uncured wood and has no cracks extending through the entire longitudinal length thereof.
 4. A plug as in claim 3, wherein the wooden member is made of wood having a density at least as great as that of fresh cut pine.
 5. A plug as in claim 2, further including a collar of moist clay surround at least a portion of the flared section.
 6. A plug as in claim 2, further including shoulders formed at the junctions of the flared section with the enlarged end and the intermediate section; and a collar of moist clay surrounding the flared section, between the shoulders.
 7. A plug as in claim 6, wherein the shoulder at the junction between the flared section and the intermediate section is turned to more securely hold the clay collar. 